A strong and persistent ridge of high pressure aloft (GOES water vapor image animation) along with a northward push of unusually warm air behind a poleward-moving frontal boundary (GOES IR image animation) helped some locations in Alaska set all-time record high temperatures for the month of January (including 51Âº F at Nome and 52Âº F at Denali National Park). An AWIPS I image comparison of 1-km resolution Suomi NPP VIIRS 0.64 Âµm visible channel data and the corresponding false-color Red/Green/Blue (RGB) product at 23:57 UTC on 27 January 2014 (above) showed generally cloud-free conitions over much of the northwestern quarter of Alaska — at that time Nome (station identifier PAOM) had a surface air temperature of 50Âº F, with offshore (east-northeasterly) winds. The Nome airport reported a snow depth of 12 inches on the morning of 27 January — however, there were several areas of bare ground (which appear as shades of cyan in the RGB image) scattered across the Seward Peninsula. Snow and ice appear as varying shades of red on the RGB image; supercooled water droplet clouds appear as shades of white, with ice crystal clouds taking on a pink to lighter red hue.

About an hour and a half earlier (22:14 UTC on 27 January), a closer look at the Seward Peninsula region using AWIPS II full-resolution (250 meter) Suomi NPP VIIRS visible and false-color RGB images (below) showed even more detail in terms of the location and size of the bare ground areas, with a few upwind of Nome (which was located approximately in the center of the images). Full sunshine and winds blowing across areas of snow-free ground likely helped to warm the air that was moving toward Nome. In addition to setting the all-time January high temperature of 51Âº F, the morning low that day of 38Âº F was also the warmest January minimum temperature on record for Nome.

AWIPS II images of 375-meter resolution Suomi NPP VIIRS 0.64 Âµm visible channel data (above) showed the growth of new ice immediately offshore in the northwestern portion of Hudson Bay, Canada during the 17 November – 19 November 2013 time period. The northwesterly flow of cold arctic air in the Arviat, Nunavut (station identifierCYEK) region was also producing well-defined cloud streets over the open waters of Hudson Bay.

The corresponding false-color “Snow Cloud Discrimination” Red/Green/Blue (RGB) images (below) confirmed that the brighter white nearshore features seen on the visible images were ice — ice and snow cover appear as shades of red on the RGB images, in contrast to supercooled water droplet clouds which appear as varying shades of white.

Suomi NPP VIIRS “Snow Cloud DIscrimination” false-color RGB images

On 18 November, a significant amount of young pack ice motion can be seen in the 104-minute period between the 17:16 UTC and 19:00 UTC VIIRS visible images (below).

Hat tip to Mark Ruminski (NOAA/NESDIS) for directing our attention to a pair of airborne glacial silt plumes that were being drawn southward over the far northern Gulf of Alaska on 16 November 2013. McIDAS images of GOES-15 0.63 Âµm visible channel data (above; click image to play animation) showed the two distinct hazy plumes as they were being advected offshore east of the Cordova, Alaska (PACV) area. The tight cyclonic circulation of a mesoscale area of low pressure may have helped to increase the speed of the gap winds that were lofting the glacial silt particles from the Copper River Delta and Icy Bay regions.

Suomi NPP VIIRS 0.64 Âµm visible channel images

AWIPS images of Suomi NPP VIIRS 0.64 Âµm visible channel data (above) showed a better view of the 2 plumes at 21:23 and 23:04 UTC. The airborne glacial silt plumes appeared darker on the corresponding 3.74 Âµm shortwave IR images (below) due to enhanced solar reflection off the small particles.

Suomi NPP VIIRS 3.74 Âµm shortwave IR images

MODIS Volcanic Ash Height product

MODIS-based products designed to monitor volcanic ash plumes were also able to detect the glacial silt plumes and provide quantitative information about these features. The mean plume height (above) was around 5000 feet, with a maximum around 9000 feet at some locations. The mean particle effective radius (below) was generally in the 4-7 Âµm range, with a maximum size of 9-10 Âµm.

GOES-15 0.63 Âµm visible channel images (above; click image to play animation) showed a distinct hazy plume streaming southeastward from the Katmai volcano area in Alaska on 22 September 2013. This was a signature of re-suspended volcanic ash — a deep layer of ash has remained on the ground near the volcano following the massive 1912 eruption — which was carried aloft by strong winds on the back side of a deep area of low pressure over the Gulf of Alaska (below).

Suomi NPP VIIRS 0.7 Âµm Day/Night Band image

A closer view using a sequence of four Suomi NPP VIIRS 0.7 Âµm Day/Night Band images (below) showed the evolution of the ash plume as it moved over southeastward over Kodiak Island and then out over the Gulf of Alaska. Winds at Kodiak (station identifier PADQ) gusted as high as 55 knots or 63 mph. With limited snow cover and strong winds (which were enhanced by local terrain effects), the surface volcanic ash was easily lofted to great heights.

Suomi NPP VIIRS 0.7 Âµm Day/Night Band images

An image of a MODIS-based NOAA/STAR/CIMSS Volcanic Ash Height product is shown in combination with the Volcanic Ash Advisory that was issued by the Anchorage Volcanic Ash Advisory Center (below).

MODIS Ash Height product with Volcanic Ash Advisory

MODIS Ash Height product

A sequence of three MODIS Volcanic Ash Height product images (above) suggested that the average height of the re-suspended ash plume was around 9,000 – 11,000 feet. A vertical profile of CALIPSO satellite-based lidar data near the source of the ash plume (below; courtesy of Mike Pavolonis, NOAA/NESDIS/STAR) indicated that the top of the plume was around 3.5 km or 11,000 feet (at 12:57 UTC, near latitude/longitude 58 N / 155 W).

CALIPSO total attenuated backscatter

The corresponding MODIS Ash Mass Loading product (below) indicated values of 2-3 tons per square kilometer existed over much of the ash plume.

MODIS Ash Mass Loading product

Finally, the corresponding MODIS Ash Mass Effective Radius product (below) showed that much of the plume likely consisted of particles with radii in the 4-6 Âµm range, with a maximum value of 8.33 Âµm.

MODIS Ash Mass Effective Radius product

Additional information on the NOAA/UW-CIMSS GOES-R Volcanic Ash Products shown above can be found in this Java-based VISITview lesson(a separate Lesson Playback Control window will open to assist in viewing the lesson content).

===== 23 September Update =====

Suomi NPP VIIRS 0.7 Âµm Day/Night Band image

On the following day (23 September), a Suomi NPP VIIRS 0.7 Âµm Day/Night Band image (above) showed that the resuspended Katmai ash plume was still present, but was much less expansive than what was seen on 22 September.

Hat tip to Mark Ruminski of the NOAA/NESDIS Satellite Services Division for bringing this interesting event to our attention!